We’ve heard it in the workplace or at school. We’ve said it to friends and co-workers.

“Don’t worry, I’m not contagious anymore.”

What’s the Difference Between Viral and Bacterial Infections?

While both viral and bacterial infections have similar symptoms and are considered contagious diseases, they’re different when it comes to transmission and treatment.

Viral infections are caused by viruses, which are a type of microorganism that invade the cells of your body. Unlike bacteria, viruses can’t survive without a host, such as a human, and they’re antibiotic resistant. However, antiviral medication can help your body clear some viruses.

Bacterial infections are caused by bacteria, which are organisms with a single cell that can reproduce on their own. Bacteria survive in many environments, like the human body and countertops. Antibiotics can treat most bacterial infections. 

When Am I Contagious?

“A cough or a fever aren’t the only indications of being contagious,” explains Dr. Anderson. “You’re contagious before you have symptoms — during the incubation period, when the virus enters your system.”

And just because you feel better doesn’t mean those around you are safe. In fact, you’re still contagious after symptoms subside, carrying a bacterial or viral infection that can spread to others. If you’ve had a recent illness, avoid physical contact with others, specifically children and older adults, and avoid preparing food for others.

Contagion Timeline for Common Conditions

Here’s how long common viruses and bacterial infections are typically contagious before and after symptoms start.

Norovirus (stomach flu, more common in adults)

• Time you are contagious before symptoms start: 10 to 50 hours
• Time you are contagious after symptoms start: 24 to 60 hours
• Time it can take before you are not contagious: One to three weeks as this virus can continue to be shed in poop after symptoms stop

Rotavirus (stomach flu, more common in children)

• Time you are contagious before symptoms start: One to three days
• Time you are contagious after symptoms start: Two to four days
• Time it can take before you are not contagious: One to three weeks as this virus can continue to be shed in poop after symptoms stop

Influenza (flu)

• Time you are contagious before symptoms start: One to four days
• Time you are contagious after symptoms start: Three to 14 days

Rhinovirus (common cold)

• Time you are contagious before symptoms start: One to four days
• Time you are contagious after symptoms start: Three to 14 days

SARS-CoV-2 (COVID-19)

• Time you are contagious before symptoms start: Two to three days
• Time you are contagious after symptoms start: Two to 14 days

Respiratory syncytial virus (RSV)

• Time you are contagious before symptoms start: One to two days
• Time you are contagious after symptoms start: Three to eight days (According to the CDC, some infants and people with weakened immune systems can continue to spread RSV for four weeks or more after they stop showing symptoms.)

Streptococcal pharyngitis (strep throat)

• Time you are contagious before symptoms start: Two to five days
• Time you are contagious after symptoms start: 24 to 48 hours if you are taking antibiotics, two to three weeks if you are not taking antibiotics

Prevention, Prevention, Prevention

Prevention is the most effective way to protect you and your family from viral and bacterial illnesses. Dr. Anderson shares three simple habits that can help you avoid illness and stop the spread if you become sick:

• Wash your hands frequently.
• Avoid touching surfaces in public.
• Cover your mouth and nose when you cough or sneeze.